The invention includes a drive mechanism arranged in an actuator housing. The drive mechanism comprises an electric motor and a drive train, an input part of the drive train being coupled to the output shaft of the electric motor, and an output part of the drive train being coupled to a driven part.
Such a mirror adjustment mechanism is known from, for instance, patent publication EP 0 675 817, in which a first actuator part is attached, by means of a friction coupling, to a base plate which is fixed relative to the bodywork of the motor vehicle, while a second actuator part forms the driven part to which the output part of the drive train is coupled. By activating the electric motor, the second actuator part pivots relative to the first actuator part, so that the mirror housing, which is attached to the second actuator part, is adjusted. Accordingly, from the driver's space, the user of the motor vehicle can have the mirror housing fold in or fold out between an operative position, in which the mirror housing is oriented substantially transversely to the bodywork, and a folded-in position, in which the mirror housing is oriented rearwards and alongside the bodywork. For instance during parking maneuvers, the driver can then, for the purpose of reducing the width of the vehicle, bring the mirror housing from an operative position to a folded-in position. During the electrical adjustment of the mirror housing, the position of the first actuator part can remain unchanged relative to the base plate. Upon reaching an end position, such as an operative position or a folded-in position, the mirror housing cannot pivot any further relative to the bodywork.
In order to force a pivoting movement between the first and second actuator part, the electric motor in this situation overcomes a frictional force of a friction coupling, so that the first actuator part starts to pivot relative to the base plate. After pivoting through a select or predetermined angle, the electric motor is switched off in that an electrode structure provided between the first actuator part and the base plate breaks an electrical connection between the electric motor and an electrical supply.
To improve the reliability of operation of the friction coupling, the coupling may be provided with a lubricant, such as for instance grease. However, since electrical circuits are present in the proximity of the coupling, use of the lubricant is undesired. Moreover, when lubricant comes into contact with the electrical circuits, it is not inconceivable that, as a consequence, the circuits function less well or even do not function at all anymore. Further, the operation of friction couplings at low temperatures is not properly guaranteed. Moreover, in certain situations, the electrode structure between the first actuator part and the base plate entails a complex succession of switch control operations of the electric motor, for instance when the mirror housing has been manually brought from the folded-in position to the operative position.
An object of the invention is to provide a mirror adjustment mechanism of the type mentioned in the opening paragraph hereof, in which some or all of the challenges mentioned are avoided while maintaining advantages. An object of the invention is to obtain a mirror adjustment mechanism with which the electric motor is switched off when an end position is reached, without the use of a friction coupling. To that end, the drive mechanism includes a driving part connected to an electrical circuit, arranged so as to be movable under spring action relative to the actuator housing, while the driving part, for controlling the electric motor, further comprises at least one first electrical contact part which cooperates with at least one second, corresponding contact part fixedly arranged with respect to the actuator housing and connected to the electrical circuit, the driving part being movable between a first position in which the impedance between the first and second contact parts has a first value, and a second position in which the impedance between the first and second contact parts has a second value.
What may be achieved by moving, upon the end position being reached, the driving part included in the drive train against a spring action relative to the actuator housing, and thereby varying the electrical impedance between the first contact part connected to the driving part and the second contact part arranged fixedly with respect to the actuator housing, is that the impedance between the electrical circuit and the first contact part varies when the mirror housing reaches the end position. Through variation of the electrical impedance, the electric motor can be switched off without performing or requiring additional switching operations.
What can be further achieved is that, by moving the driving part against a spring action, a spring force is exerted on the driving part and hence also on the drive train in which the driving part is included, thereby preventing displacements of the drive train and the driven part coupled thereto. The driven part can be formed, for instance, by the mirror housing or by a part which cooperates with parts connected fixedly to the bodywork of the vehicle, such as, for instance, a pivot. In both embodiments, movements of the mirror housing, such as shocks and vibrations, are counteracted by this spring force.
Also when external forces are exerted during adjustment of the mirror housing, the electric motor will be switched off as a result of displacement of the driving part relative to the actuator housing. This occurs, for instance, when the mirror housing is blocked by an object outside the vehicle, for instance a pillar.
An additional potential advantage of moving the driving part against a spring action is that when the mirror housing is adjusted from the end position or a blocked position the electric motor does not need to produce any additional energy to disenable any clamping coupling that may be present. This lowers requirements regarding the power to be produced by the electric motor at the beginning of an adjusting movement. The beginning of the movement to be performed by the mirror housing will be induced by the power produced by the energized electric motor, but additionally so by the spring action.
What is achieved by attaching the driving part to the actuator housing with at least one spring element, is that movement of the driving part only occurs when the force that is to be produced to adjust the mirror housing is greater than the force for moving the slide against the spring action.
When the electric motor is switched off, the mirror housing can then be secured in the end position with a spring force which is at the least equal to the bias of the spring element.
The driving part may be included in the drive train, so that the mirror housing has some clearance when a self locking electric motor is used. If clearance is not desired, it may be elected to include the driving part in the electric motor, so that the user of the motor vehicle, by exerting forces on the mirror housing, cannot feel any clearance resulting from the moveably arranged driving part.
In an embodiment, the driving part comprises a slide which cooperates with a driving element. In this way, movements of the driving part are uncoupled into, on the one hand, rotations or translations forming part of movements of the drive train that occur during normal use when adjusting the mirror housing and, on the other hand, the movement of the driving part when reaching the end position. Such uncoupling enables the slide and the drive element to be optimized each separately for their specific function.
What is achieved by designing the slide to be movable along a guide path, is that the sliding movement may be better defined in a properly reproducible manner, which can be beneficial to the reliability of the mirror adjustment mechanism.
It is noted that the Japanese patent publication JP 1 022 646 describes a mirror adjustment mechanism for adjusting a mirror housing which has a driving part which is arranged so as to be movable under spring action relative to an actuator housing. Upon the mirror housing reaching an end position, the driving part moves against the spring action, so that the motor of the mirror adjustment mechanism is cut off. The driving part is arranged between two helical springs.
Furthermore, it is noted that the Japanese patent publication JP 8 119 037 describes a similar mirror adjustment mechanism, with a driving part arranged between two helical springs.
In an embodiment according to the invention, the driving element is rotatably bearing mounted in the slide. As a result, an elegant, robust coupling is obtained between, on the one hand, the driving element which during normal operation performs a rotating movement and, on the other hand, the moving slide.
The first and second contact parts in the first position can jointly form an electrical connection, so that the impedance is low, and in the second position form an open pair of terminals, so that the impedance is high. What is thereby achieved is that a displacement of the driving part has as a result of an electrical connection between the first and second contact parts is broken or, conversely, established. In this way, the electric motor can be switched off. By connecting the electrical circuit, to which the second contact part is connected, directly with an electrical supply, the electric motor can be switched off directly upon movement of the driving part. By including a separate control circuit in the electrical circuit, the motor can also be switched off indirectly, for instance by switching off the supply after detection of impedance variation between the contact parts. Instead of a substantially resistive impedance, an impedance of which the variations are substantially capacitive or inductive can be used.
The invention also relates to a wing mirror unit and to a method for adjusting a mirror housing of a motor vehicle.
Further embodiments of the invention are embodied in the appended claims.
The Figures are only schematic representations of embodiments of the invention. In the Figures, identical or corresponding parts are indicated with the same reference numerals.